You taste your kombucha: it either opens your mouth like a very strong vinegar, or it still tastes almost unchanged like sweet tea. There seems to be a “perfect point” in between … but it’s hard to reach when you’re just starting out.
Rest assured: Kombucha that is too sour or too sweet is neither a disaster nor a sign that you are “bad at fermenting”. It is merely proof that your culture is alive and that you still need to tame a few parameters: Fermentation time, temperature, sugar content, amount of starting liquid, size of the SCOBY, volume of the jar….
In this guide, we will jointly :
Why kombucha turns sour or stays sweet
How to make up for a batch that is too sour or too sweet
how to adapt your next attempts to regularly find “your” good balance
how healthy cultures (such as a well-balanced living SCOBY of the type offered by Natural Probio) facilitate this adaptation in everyday life
The aim: to make this drink a constant pleasure, rather than a lottery where every glass is a total surprise.
1. understand the balance between sugar and acid in kombucha
To know what to do, you need to understand what is really going on in your glass.
1.1 Sugar as fuel for yeast
To start, prepare a sweetened tea. This sugar is not just for flavour; it is the main food for the yeast in the SCOBY and in the starting liquid.
These yeasts :
consume sugar
produce alcohol and CO₂.
leave behind compounds that are then metabolised by bacteria
As long as there is still a lot of sugar left, you are still very close to a sweet iced tea, with a slowly starting fermentation.
1.2 Bacteria as architects of acidity
Bacteria (mainly acetic acid bacteria, sometimes also lactic acid bacteria) then take over the work. They process :
the alcohol produced by the yeast into organic acids (acetic acid, gluconic acid, etc.).
the environment of the glass, which gradually becomes more acidic
It is this acid that :
indicates the character “Kombucha
protects the beverage from many unwanted microorganisms
brings a feeling of freshness and “fermented drink” with it
The longer you leave the glass, the more acids accumulate and the sugar content decreases: Kombucha tips from the “lightly sweetened, sparkling tea” side to “very vinegary drink”.
1.3 Your taste lies somewhere in between
There is no universal “right” acidity level. Some like their kombucha very sweet, others love it almost like apple cider vinegar.
So your task is to find out:
at which point of fermentation you like the flavour best
how long it takes to reach this point in your home at the current time of year
how you can reproduce this result regularly
Kombucha that is too sour or too sweet is not a failure: it is a clue for adjusting the next batch.
2. recognising Kombucha that is too sour… or simply well-fermented Kombucha
Before you try to “correct” him, you should be sure that he really is too angry for you.
2.1 Signs of a simply good sour Kombucha
A well-fermented Kombucha presents :
a vinegary but clean odour (apple cider vinegar, green apple, white grapes)
a distinctly sour flavour that stimulates salivation but does not sting
an almost complete absence of sugar or only a sweet background
Slight heat in the throat, but no pain
If you like it rather sweet, this step may already seem “too advanced”, but that’s not a safety issue: it’s a matter of preference.
2.2 Signs that it is too acidic for your purpose
Kombucha is more likely to be described as “too sour” if :
You grimace at the very first sip
you have the feeling of drinking almost pure vinegar
you do not even notice the tea or the initial flavours
you find it impossible to drink it without diluting or refining it
At this point, the drink is still healthy, but hard to enjoy as it is. The good news: it’s not lost yet.
3. what to do with overly acidic kombucha?
Instead of throwing it away, you can give this sophisticated Kombucha a second life.
3.1 Turn it into homemade “kombucha vinegar”
A very sour kombucha makes an excellent vinegar:
for salads, instead of apple cider vinegar
to deglaze a pan
For marinating vegetables or tofu
to flavour a sauce
All you have to do is :
Store it in a clean, closed glass bottle at room temperature or slightly chilled
leave it to mature for a few more weeks if you want a rounder profile
use it like any other mild vinegar
Many people even deliberately grow a very sour kombucha for this purpose.
3.2 Dilute it into a “tonic” drink
Another option: Dilute your overly sour kombucha in :
Still or sparkling water
an apple or grape juice or a mixture of juices
a chilled herbal tea (mint, verbena, hibiscus…)
Example:
1/3 very sour kombucha
2/3 sparkling water + lemon juice or a little honey
You get a revitalising drink that is less aggressive but still rich in organic acids.
3.3 Use as a basis for a second fragrant fermentation
You can also use this very sour Kombucha as a base for a second bottle fermentation, with :
Fruit (raspberries, apple pieces, citrus fruit)
some sugar, honey or syrup (ginger, agave…)
Spices (fresh ginger, cinnamon, cardamom)
Added sugar :
is not only there to sweeten
also serves as fuel for the remaining yeast
makes it possible to gain effervescence and aromatic complexity
The finished drink will appear less sour due to this sweetness and the fruit flavours.
3.4 Use it in the kitchen and for home care
A very sour kombucha can also serve :
For deglazing roasted vegetables
For marinating red onions, radishes and carrots
replace part of the vinegar in quick pickles
as a diluted hair conditioner (if you are used to it and your scalp can tolerate it)
In this way, every drop can be upgraded, even if the original glass seemed “unsuccessful” to you.
4. how can I prevent it from becoming too acidic in the future?
As soon as this batch has been recycled, the next step is prevention.
4.1 Shorten the fermentation time slightly
The simplest lever you can adjust is the fermentation time of your next batch.
Example:
If you have left 12 days and it is too sour, try 8-9 days.
If you are in the middle of summer and the temperature in the kitchen is 26-28 °C, you should know that everything goes faster: a kombucha that took 10 days in winter may be ready in 6-7 days.
The best reflex: Don’t wait for the “theoretical date”, but try every day from the 5th or 6th day.
4.2 Regular tasting to learn the flavour curve
From the 5th day :
take a teaspoon of Kombucha
Taste and note down your impressions (sweet, sour, vinegary…)
Repeat every day until you really like the flavour
In 2-3 tours you will get a very clear overview of :
how many days it takes to reach your equilibrium
how it changes depending on the season
when you should bottle for the second fermentation
4.3 Playing with the amount of starting fluid
The more acidic starting liquid (kombucha from a previous batch) you use, the :
the environment is sour from the start
there are many bacteria
Acidification takes place quickly
If your kombuchas are consistently too sour, you can :
stay within the recommended low range (about 10 % of the total volume)
Avoid more than 20 %, unless you deliberately want to achieve a very vinegary result
In contrast, cultures offered by specialists such as Natural Probio are supplied with a well-dosed starting liquid, which facilitates a balanced start and limits such excesses.
4.4 Monitor the temperature
Fermentation slows down below 20 °C, above 26-28 °C it gets out of hand.
To maintain finer control :
Keep the glass away from heat sources (oven, radiator, direct sunlight)
Choose a location where the temperature is relatively stable
Try earlier and more often in very hot weather: 5-7 days may be sufficient
5. too sweet kombucha: understanding what’s going on
Conversely, it can happen that :
Kombucha tastes almost exactly like the original sweetened tea
You only feel a tiny hint of acidity or nothing at all.
the SCOBY does not seem to be working
This is not just a question of flavour: it means that fermentation has not yet started properly or has slowed down considerably.
5.1 Signs of a simply “young” Kombucha
If you try very early (D+2, D+3), it is normal that :
the sugar is still well present
the acidity is very light
the development is inconspicuous
That’s no problem: you just have to wait a few more days.
5.2 Signs of kombucha that is not fermenting sufficiently
You are more likely to speak of “too sweet” kombucha (on the fermentation side) if after 7-10 days :
the flavour remains almost the same as with sweetened tea
the liquid is not more acidic
there are no or only very slight yeast deposits on the bottom
a new disc does not really form on the surface (new SCOBY)
In this case, there is a real problem with the fermentation and you need to do something about it.
6. how can you make up for a Kombucha that is too sweet?
Fortunately, a Kombucha that is too sweet still offers good scope.
6.1 Check the basic requirements
Above all, check :
The temperature: If the temperature in the kitchen is 18 °C, fermentation will proceed slowly. In this case, leave it for longer, sometimes up to 14-20 days.
The position of the jar: not in the fridge, not in a freezing cold place, not stuck to a very cold window in winter.
The covering fabric: It must breathe (not an airtight lid) and at the same time keep insects out.
Sometimes it is enough to simply place the jar in a warmer corner and wait a few days longer.
6.2 Prolonging the fermentation
If all conditions appear to be correct, the first solution is simple:
to ferment longer
sample every two days to monitor the development
You will often see that the sugar gradually decreases until you find a balance point.
6.3 Increase the initial acidity
If fermentation is still very slow to start, it may be that :
you have not added enough acidic starting fluid
Their starting fluid itself is quite soft and not very protective
To correct this, you can :
Keep slightly more acidic kombucha from another batch
use it as a starting liquid (10-20 % of the volume) for the next batch
or start with a culture in which the SCOBY and the starting liquid have been designed to ensure sufficient initial acidity
A healthy, well-acidified base offers a much better chance of getting fermentation going quickly.
6.4 Checking the condition of the SCOBY
A kombucha that remains sweet despite fermenting for days can also be a sign that :
the SCOBY is tired, weakened or almost inactive
it has been damaged by cold (stay in the refrigerator) or heat
it has received too little food for too long (batches far apart in time)
In this case you can :
separate the layers of SCOBY and start again with a younger, lighter, softer layer
start a small resuscitation test in a jar with a smaller volume to see if it produces a new disc and acid
or decide to start with a fresh, lively SCOBY to save yourself weeks of trial and error
7. adapt the next batches: Simple method to stop making mistakes
Rather than enduring acid or sugar, you can use a small home method.
7.1 Keep a mini fermentation book
Take a notebook or a note in your mobile phone and enter :
the start date of the batch
the approximate room temperature (or the season: winter, mid-season, summer)
the type of tea used (black, green, blend)
the amount of sugar (per litre)
the amount of starting liquid (% of the volume)
Then every day from the 5th day:
try a small spoonful
note: very sweet, sweet, semi-sweet/semi-acidic, well acidic, very acidic
Determine the day on which it is “perfect” for you.
Within a few batches you will recognise a pattern: e.g. “In summer I like my Kombucha at T+6, in winter rather at T+9”.
7.2 Select an interval for the “ideal range”.
Instead of targeting a specific day, give yourself a range :
For example: “Between the sixth and eighth day is perfect for me”.
Fill within this window according to your schedule and your wishes.
This way, you won’t get stressed if you can’t stow away on exactly the right day, and you’ll stay in an area that suits you.
7.3 Adjusting the secondary fermentation time
Remember that :
the first fermentation serves to create the acid base
the second fermentation (in the bottle, with a little sugar or fruit) serves to develop the sparkle and flavours
If you are bottling a still slightly sweet kombucha, the second fermentation :
will consume this sugar
will produce more gas
will increase complexity
If you are bottling an already quite sour kombucha, you can :
Add a little sugar, juice or fruit
allow a second, shorter fermentation so as not to go into extreme acidity
8. special cases: When acid or sugar appear “moody”
Sometimes the result varies from one batch to the next, even with the greatest care. Here are a few clues to help you understand.
8.1 Changes to tea or sugar
A more tannic, stronger tea or a more wholesome sugar (Muscovado type) can have an influence:
the fermentation speed
the perception of acidity
the aromas (rounder, more caramelised, more tannic)
If you change your tea or sugar type, make a note of this in your notebook and allow for a few batches of adjustment.
8.2 Size and vitality of SCOBY
SCOBY :
very voluminous, old and thick
very young, fine and light
… does not work in quite the same way. A big old SCOBY can turn sour very quickly; a young SCOBY needs a little longer to establish itself, especially at the beginning.
In order to maintain stability, some :
a moderately large SCOBY
a kind of “SCOBY hotel” next door, where the surplus records wait in very sour kombucha
8.3 Temperature differences from room to room
A simple shift of the glass can make a big difference:
on a work surface near the oven, then it will be warmer
in a kitchen corner near a cold window, it is slowed down
on the top of a refrigerator, the heat generated can reduce the speed of the refrigerator.
The same applies here: observe and adapt: If a new location systematically produces Kombuchas that are too acidic in a short time, shorten the time or change the location.
9. frequently asked questions: Sour, sweet … and everything in between
9.1 Is it dangerous to drink very sour kombucha?
In general, a very sour, clean kombucha that does not smell musty or chemical is not dangerous in itself; it is just very powerful in the mouth. Some people dilute it or drink it in small quantities.
However, if the acid is mixed with :
Suspicious odours (musty, eggs, chemical)
of visible mould on the surface
… must be thrown away without hesitation.
9.2 Can I add sugar to a Kombucha that is too sour to make it softer?
Yes, but this does not “eliminate” the acidity: it merely balances it out with more sweetness. You can :
Add a little sugar, honey or syrup
Mix with a fruit juice
Initiate a second bottle fermentation with fruit
This often results in a more harmonious drink, especially if you like flavoured kombucha.
9.3 My kombucha remains sweet despite 10 days: do I have to throw it away?
Not necessarily. Ask yourself these questions first:
Is the temperature very low?
Have I used enough acidic starting fluid?
Does my SCOBY seem to be alive (formation of a new layer, presence of yeasts)?
If everything is OK, allow a few more days to pass and try again. If nothing really happens after 14-20 days, it may be time to check the condition of SCOBY and start again with a stronger culture if necessary.
9.4 Can I mix a Kombucha that is too sour with a Kombucha that is too sweet?
Yes, that’s actually a good tip :
mix one part very sour Kombucha with one part still sweet Kombucha
try and adjust the ratio until you find the point that you like
bottle it, possibly with light flavours (fruit, plants), for a second fermentation
You get a balanced drink and avoid waste at the same time.
9.5 Does a good quality SCOBY really help to stabilise all this?
A healthy SCOBY with a balanced ratio of yeasts and bacteria, together with a high quality acidic starter liquid, makes a huge difference:
Fermentation starts faster and more evenly
the development of flavour is more predictable
you have less extreme deviations from one batch to the next
This is the advantage of starting from a serious crop prepared by professionals and not from a SCOBY salvaged under unsafe conditions. If the base is solid, it is much easier to adjust the acidity and sugar content.
Conclusion: From a “problem” to a tool for learning your kombucha
Kombucha that is too sour or too sweet is not an end in itself, but a message that your drink is sending you:
Too acidic: fermentation time too long for your taste, high temperature, very acidic starting liquid, very active SCOBY
too sweet: slow fermentation, low temperature, lack of acidic starter liquid, weakened SCOBY or sub-optimal conditions
By learning :
Try regularly
make a note of your observations
Adjust the duration, temperature and quantity of the starting fluid
also upgrade “imperfect” batches (dilution, cooking, second fermentation, homemade vinegar)
… Turn your mistakes into experience. Batch by batch, you approach the moment when you lift the fabric, try it and say: “Now it’s just the way I like it”.
With a healthy and robust starter culture, a balanced live SCOBY and a clearly acidified starter liquid, as offered by specialised suppliers of artisan Kombucha, this learning curve becomes even smoother. You will no longer have the feeling that your kombucha is “living its own life” without you, but on the contrary, it will respond to your gestures and attitudes and eventually find its place naturally in your everyday life.
